Scanning light control for pinhole detectors



.1. w. HAGS Feb, '19, 1946.

scANNING LIGHT coNTRoLFoR PIN HOLE DETECTORS I Filed April 25, 1944 5 Sheets-Sheet l Feb. 19, 1946. J 'w HAGS 2,395,181

SCANNING LIGHT CONTROL FOR PIN HOLE DETECTORS Filed April 25, 1944 l 5 sheets-sheet 2 INVENTOR dosfpHW/JAGS,

v by' i Feb.v 19, 1946. J. w. HAGs 2,395,181

SCANNING LIGHT CONTROL FOR PIN HOLE DETECTORS Filed April 25, 1944 5 Sheets-Sheet 5 w Isla INVENTOR dosfpHl//AGS,

y /ws AMD/weg l l Z Y J. W. HAGS SCANNING LIGHT CONTROL FOR PIN HOLE DETECTORS Filed April 25, 19214 5 sheets-sheet 4 Feb. 19, 1946.

J. W. VHAGS SCANNING LIGHT CONTROL FOR PIN HOLE DETECTORS Filed April 25, 1944 5 'Sheets-sheet 5 Patented Feb., 1e, 1946 SCANNING LIGHT CONTROL FOR PINHOLE DETECTORS Joseph W. Hags,

Carnegie-Illinois tion of New Jersey Swissvale, Pa., assgnor to Steel Corporation, a corpora- Application April 25, 1944, Serial No. 532,683

4 Claims. (Cl. Z50-41.5) Y

In the production of electrolytic tin plate, the operation consists essentially in electroplating a continuously rapidly moving, previously prepared steel strip of indeterminate length with a plating of tin 'a few thousandths of an inch in thickness. Since the resulting plated material is to be fabricated into cans for preserving foodstuffs, it is essential that the tin plating, although it is very thin, must cover the entire area of both surfaces of the strip and be adherent thereto throughout its extent.

Imperfections in the surface of the strip deleteriously alect the adherence of the tin plating. Areas of dirt on the strip, or of oxidation on the surface, inhibit the production of adherent plating on such areas. In addition to such., the presence of pin holes in the strip inhibits the formation of a continuous coating of tin.

The present invention relates to equipment which is employed specifically on commercial tinplating lines, although obviously it has a Ymuch wider use, as will become apparent. Such equipment for the processing of the strip, usually includes an automatic pin hole detector. Such devices are arranged so that a series of lights shines on the surface of the moving strip. The lights are mounted in a scanning head unit built so that the light shines only through a long narrow aperture in the bottom, the aperture being about the same length as the Widest strip to be processed. Below the scanning head there is located an enclosed housing in which are placed a row of photoelectrlc tubes. The strip passes between the light source andthe photoelectrie` tubesy so as to prevent light from striking any of the light sensitive tubes unless there is a hole in the strip. In order to prevent light from shining past either side of the strip and striking the photoelectric tubes, an adjustable slide usually is installed on either side of the photoelectric tube housing, which slide extends, in practice, about one and one-half inches under the sides of the strip, and is locked in place by means of a hand set screw. The slides are set by hand for the particular width of strip being processed and" they are made with an upright portion which serves to guide the strip and hold it in proper position over the pin hole detector.

The foregoing mechanism has certain disadvantages, however. Among such disadvantages, there may be mentioned, importantly, the fact that the slide curtains for the sides of the strip extend, in practice, about one and a half inches under the edge', and for that reason the edges are not inspected for pin holes over that area.

` The principal reason for having the light curtain Y theless, on most processing lines, there is considerable tension and thestrip must be allowed to float in order to prevent damage to the strip by the use of side guides.

The present invention provides equipment for the elimination of the said objections, which equipment enables the entire width of the strip, with the exception of a very narrow area along the edges, to be scanned by the light source. The invention provides a positive means of controlling the light curtain at the sides of the strip, and permits pin hole detection for practically the entire surface of the strip. In the mechanism of the present invention, there are no xed guides to the oat of the strip and all but about one-eighth inch of the edge of the strip is inspected for pin holes.

The invention lwill be understood more readily from the accompanying drawingsl in which Figures 1 and 1A, taken together, show diagrammatically certain elements which are employed in conjunction with one type of apparatus commercially employed for the production of electrolytically tinned steel strip;

Figure 2 is a plan view of a portion of the line shown in Figures 1 and 1A, at the No. 1 pin hole detector, shown on Figure 1, the improvements of the present invention being installed on the apparatus at this location;

Figure 3 is a sectional elevation, taken on the line IIL-III, Figure 2, looking in the direction of the arrows;

Figure 4 is a side elevation of the apparatus shown in Figure 2;

Figure 5 is an enlarged plan view, showing contact point of the carriage of the present invention with the strip;

Figure 6 is a sectional elevation taken on the line VI-VI of Figure 5, looking in the direction of the arrows;

Figure 7 is a fragmentary elevation showing further details of the carriage of the present invention, the view being taken on the line VII-VII of Figure 5, looking in the direction of the arrows;

Figure 8 is a transverse sectional elevation of the apparatus, the view being taken on line` equipment,

VlII-VIII of Figure 5, looking in the direction of the arrows; and Y Figure 9 is a further transverse sectional elevation of the apparatus of the present invention, the

view being taken on the line IX-IX of Figure 5, looking in the direction of the arrows.'

Referring more particularly to the drawings, it is thought that Figures 1 and 1A require no discussion in view of the self-explanatory legends applied thereto. It will be noted therefrom, however, that there are two pin hole detectors, No. 1 being at the so-called off-weight gage drag bridle" and No. 2 (Figure 1A) being just after the melting furnace wherein the plated tin is melted to increase uniformity of finish of the completed coating, and to some extent, the bond between the strip itself and the coating. At each of the pin hole detectors, there are mounted cooperating carriages of the present invention for securing and guiding the strip while enabling the source of light at each detector to scan substantially the entire sheet.

The pin hole detectors are standard pieces of and include photoelectrie tubes mounted in housing II, (Figure 4), lights being located overhead in scanning head I3, the strip I5 passing between the housing II and the scanning head I3 so that light passing through any holes in the strip flashes upon the photoelectric tubes to actuate the same instantaneously at j intervals corresponding to the presence of such pin holes. It may be noted that the No. Al pin hole detector which is located in the line ahead of the plating equipment is, in practice, electrically connected to a pin wheel mechanism on the drag bridle. bridle rolls and is geared so that it makes less than one revolution while the strip travels from the pin hole detector to the olf-weight piler. When a hole in the 'strip passes the detector, an electrical impulse causes one pin in the revolving pin wheel to be pushed out of position. An adjustable contact is set so that the pin which has been pushed out of position closes that contact when the pin reaches it, and causes the gate in the off-weight piler to open. 'The pin wheel mentioned usually has 48 to 96 pins depending on the accuracy desired. The adjustable contact is set so that the contact is closed at the correct position in the travel of the strip, which .in this case, is

when the defective portion of the strip has reached the gate into the off-weight piler. The gate is solenoid operated, and the adjustable contact and a timing device are set so that the gate remains open a sulcient length of time to direct the defective sheet into the piler and usually at least one sheet one each side of it. A11 sheets which thus are rejected automatically into this piler are later inspected manually, and the prime sheets recovered.

The No. 2 pin hole detector is employed to detect any holes not completely covered by the plating, or any holes punched through the strip by arcing during travel of the strip through the plating cells. The pin wheel for this detector, which controls the operation of the classifier gate into the oil-weight piler, islocated at the flying shear and is driven by the shear leveler.

The foregoing constructions constitute standard equipment and do not form any part of the present invention. Consequently they are not shown in the drawings, and reference thereto is made merely by way of explanation of how a pin hole detector mechanism may be constructed and oper- This pin wheel revolves with the drag ated, in view of the fact that the present invention ls associated with such mechanism.

The present invention is directed to the carriages I'I and I9 and the carriage track 2|. Carriages I1 and I9 are similar in construction. and, hence only one of these needs to be referred to in detail. y l' Carriage I1 is equipped with a small antifriction bearing 23 against which the strip I5 travels. Bearing 23 is mounted on pin 25 which has a shank 21 threaded at its end for reception of a nut 28. The shank 21 receives a holder, which conveniently is composed of the phenolic condensation material known to the trade under the registered trade-mark Micarta," which trademark is registered by the Westinghouse Electric and Manufacturing Company at Pittsburgh, Pennsylvania.

The holder 29 retains an upper guide plate 3l in position, this guide member having a recess and a hole extending therethrough, whereby it may be slipped over the shank 21 of the pin 25 and rests on shoulder 33 of the pin 25, the bearing 23 being received in the recess in the guide plate 3|. A top plate 35 also is received over the shank 2l of thepin 25, by way of a hole formed in the bracket, this hole being of the same diameter as that of the shank. Bracket 35 is secured to the carriage Il by cap screws 3l and is held in place on the pin by nut 28. Therefore, the assembly including the upper guide plate 3I, the holder 29 and top bracket 35 lis retained by the pin and the nut 28, and additional screws 36.

A lower guide plate 39, similar to the upper guide plate 3I is fitted over the bottom of the antifriction bearing 23 and held in place by the cap screws 36. The strip I5 engages the antifriction bearing 23 between these upper and lower guide members.

The guide plates 3| and 39 are supported by the top plate 35, and are secured to the top plate `35 by the cap screws 36, the bearing 23 being clamped between the plates. Washers 4I between the plates prevent clamping of the bearing rollers when the screws are tightened.

The carriage I1 is mounted on forward and rear pairs of rollers or wheels 45 and a bracket 41 is secured to the carriage and extends downwardly therefrom. Such' bracket may be bolted to the carriage as is indicated at 49. A flexible cable 5I is attached to the bracket and passes over a pulley 53 suitably mounted beneath the carriage I1, for example on the photocell housing. A weight 55 is attached to the end of the cable 5I and functions to hold the carriage against the edge of the strip while still permitting the carriage to move with the side travel or float of the strip.

In case narrow strip is being processed, or the strip moves from its normal path, the carriages I1 and I9 move with the strip, due'to the pull exerted by the weights 55.

is has been pointed out, carriage I9 is the duplicate of carriage II, and the same reference not accessible to the scanning lights.

The carriages I1 and I9 are mounted on a track member 5I which extends across the frame of the drag bridle and is mounted thereon by means' of brackets 65. The track member 6I has an upstanding web 61 extending along the central portion thereof, and fastened to the edges thereof are longitudinally extending strips 59, the fastening of these strips to the track member 6I being shown as being effected by screws 1I. The strips 69 in conjunction with the web 51 form the previously mentioned tracks 2| in which the wheels 45 are received and along which the said wheels travel during reciprocation of the carriages I1 and I9 responsively to sideways movement of the strip I5. In order to prevent obstruction of light passing from the light source in the scanning head I3 and the photoelectric cells in housing II, the track member 6I has an opening therein indicated at 13, whichwis in alignment with openings 51 and 59 of the carriage guide members, the strip I5 passing between the openings 51 and 59 and above opening 13.

The previously described apparatus is shown as being mounted on frame 63 of the drag bridle between the bridle rolls 15 and 11, whichalsd are mounted on the frame 63 in suitable bearings 19, BI, the rolls being driven through power applied thereto through shafts 83, 85, driven by a suitable source of power, not shown. A third roll, indicated at 81 (Figure 4) completes the said drag bridle. v

The No. 2 pin hole ldetector shown on Figure 1A operates in a similar manner to the No. 1 detector, and carriage mechanism identical with that described above is provided for the No. 2

detector.

The carriage mechanism herein described provides instrumentalities for automatically controlling the light curtain at the sides of the strip. The edges of the strip are always in contact with the outer surface of bearings 23, which turn with the travel of the strip; and, as has been pointed out above, in case narrow strip is being processed, or the strip moves from its normal path of travel, the carriages move with the strip, due to the pull exerted by the counterweights 55.

I claim:

1. Apparatus for detecting pin holes in metal strip, which comprises in combination, a source of light for scanning the width of the strip, photoelectric lcells disposed oppositely to the source of light and adapted to be energized by light transmitted thereto through pin holes in the strip, guide means for the strip extending above and below the strip, the said guide means having registering openings above and below the strip for enabling the scanning light to reach substantially the entire width of the strip while being adapted to be engaged continuously by the edges of the strip during travel of the said strip, and yieldable mum `width of the strip adjacent to the edges thereof which is shielded from light from the light source.

2. Apparatus for detecting pin holes in metal strip, which comprises in combination, a source of light for scanning the width of the strip, photoelectric cells disposed oppositely to the source of light and adapted to be energized by light transmitted thereto through pin holes in the strip, guide means for the strip enclosing the strip above and below and laterally thereof, carriage means for the'guide means, instrumentalities turnably mounting the guide means on the c arriage means, and roller mechanism enabling the carriage means to yield automatically responsively to lateral oating movements of the strip and to variations in width of the strip, the guide means covering only a minimum width of the strip along the edges of the strip, whereby substantially the entire width of the strip is scanned by light from the source thereof, the yielding roller mechanism for the carriage means causing the said covered minimum width of the strip to be maintained constant at all times for producing uniform scanning of the strip.

3. Apparatus for detecting pin holes in metal strip being processed, which comprises in combination, a source of light for scanning the width of the strip, photoelectric cells disposed oppositely to the source of light and adapted to be energized by light transmitted thereto through pin holes in the strip, carriage means at each edge of the strip adapted to be continuously engaged by the edges of the strip during travel of the strip, track means mounted adjacent to the source of light and the photoelectric cells and interposed therebetween, each of the carriage means including a body, an antifriction bearing assembly including an antifriction bearing adapted to be engaged continuously against the edges of the strip, upper and lower guide members, and meansfor locking the antifriction bearing and the guide members together, means for securing the antifriction bearing assembly to the carriage body, mounting rollers for the carriage body positioned on the said track means, and instrumentalities continuously urging the carriage means against the stripwhile permitting automatic yielding of ,the carriage means responsively to lateral movements of the strip during travel thereof, and to differences in Width of the strip being processed, the said upper carriage mechanism for the guide means enabling I the said guide means for the strip to yield automatically responsively to sideways movements of the strip during the travel `of the strip, thesaid guide means for the strip being thereby self-accommodating to variations in direction of travel of the strlpand in the Width of the strip, thereby maintaining constant under all conditions a minii and lower guide members and the track means having aligned openings therethrough for enabling passage of light from the source thereof to the strip being processed and through any pin holes in the strip to the photoelectric cells, the openings in the guide members extending almost back to the antifriction bearing, and the opening in the track means extending sufliciently far back in the track means relative to the carriage means so as to be continuously partly covered by the carriage means, the said openings being disposed to enable substantially the entire width of the strip to be scanned except for narrow widths thereof immediately adjacent to the edges of the strip.

4. Apparatus for detecting pin holes in metal.

strip being processed, which comprises in combination, a source of light forscanning the width of the strip, photoelectric cells disposed oppositely to the source of light and adapted to be energized by l light transmitted thereto through pin holes in the strip, carriage 'means at each edge of the strip adapted to be continuously engaged by the edges of the strip during travel of the strip, track means interposed between the source of light and the 4 photoelectric cells, each of the carriage meam including a body, an antitriction bearing assembly including an antitriction bearing adapted to be engaged continuously by the edges of the strip, upper and lower guide members, and fastening means for securing the antifriction bearing and the upper and lower guide members together, means for securing the anti-friction bearing assembly to the carriage body, mounting rollers for carrying the carriage body positioned on the said track means, a bracket secured to the carriage body, a. pulley mounted beneath the track means but adiacent thereto, a flexible cable attached to the bracket and extending over the pulley, and a counterwelght for the carriage means attached to the cable, the said counterweight continuously urging the carriage means and the antifrictlon bearing against the strip, while permitting automatic yielding of the carriage means responsively to lateral movements of the strip during travel thereof and to diierences in width of the strip being processed, the said upper and lower guide members and the track means havingl aligned openings therethrough lor enabling passage of light from the source thereof to the strip being processed and through any pin holes in the strip in the photoelectric cells, the openings in the guide members being substantially coextensive and extending from the forward edge of the guide members back almost to the antifriction bearing, the opening in the track means being larger than the openings in the guide members and extending sufficiently far back in the track means relative to the carriage means so as to be continuously partly covered by the carriage means in all positions thereof, the said openings' being disposed to enable substantially the entire -width of the strip to be scanned by light from the light source except for narrow widths thereof immediately adjal cent to the edges of the strip.

JOSEPH W. HAGS. 

